First randomised trial tests criteria used to diagnose heart attack

First randomised trial tests criteria used to diagnose heart attack

28 August 2018

Results presented today at the 2018 European Society of Cardiology Congress call into question the current diagnostic definition of heart attack used by medical professionals.

Professor Nicholas Mills, Centre for Cardiovascular Science, principal investigator of the High-STEACS trial, said: “These results are controversial because they suggest that the Universal Definition of Myocardial Infarction needs to move away from binary thresholds to diagnose and treat patients with myocardial infarction. It is now up to the research community to find a superior approach.”

Heart attack, also known as myocardial infarction, is one of the world’s leading causes of death. It is currently diagnosed through a combination of family history, electrocardiogram, and analysis of cardiac troponin levels. Troponin is a protein that is released into the blood when the heart muscle suffers damage, and is therefore one indicator of heart attack. According to the Universal Definition of Myocardial Infarction, troponin levels above the 99th percentile indicate that a heart attack occurred.

This study is the first randomised trial evaluating the use of high-sensitive cardiac troponin assays in diagnosing heart attacks. CVS researcher Nicholas Mills and his research team examined whether using a more sensitive troponin analysis with the 99th percentile threshold during diagnosis would lead to reduced numbers of future heart attacks or cardiovascular death one year after an initial heart attack.

Examining all patients with suspected acute coronary syndrome in ten hospitals across Scotland, the study used both a contemporary troponin assay and a high-sensitive cardiac troponin I assay to assess troponin levels of all emergency department heart attack patients. The contemporary troponin assay was used for all clinical decisions made during an initial six month validation period, after which hospitals were assigned early or late implementation of the high-sensitive troponin assay to make all future clinical decisions using the 99th percentile. Registries were used to record subsequent heart attacks or cardiovascular death up to one year after initial hospitalisation.

48,282 patients were involved in the study, 47% of whom were women. The average age was 61. 22% of patients had high-sensitive cardiac troponin I levels above the 99th percentile. The high-sensitive troponin assay reclassified 1,771 patients with heart injury or heart attack not initially identified by the contemporary assay. Of those reclassified patients, less than a third had a final diagnosis of heart attack.

Of the reclassified patients, subsequent heart attack or cardiovascular death occurred in 105 of 720 (14.6%) patients during the validation phase, and 131 of 1,051 (17%) patients in the implementation phase.

Professor Mills said: “The trial found that implementation of a high-sensitivity cardiac troponin I assay using the 99th centile as the diagnostic threshold increased the frequency of diagnosing myocardial injury or infarction. However, use of this method to help diagnose and treat patients was not associated with lower rates of recurrent myocardial infarction or cardiovascular death at one year.”

He continued: “The findings were surprising and initially disappointing. But it was encouraging that there was no evidence of misdiagnosis, inappropriate treatment, excess bleeding or harm. Indeed, the length of stay across the trial population was reduced by almost a third suggesting that use of the high-sensitivity test increased the confidence of clinicians to rule out heart disease, with benefits for health service providers.”

The High-STEACS trial was published in The Lancet, 28 August 2018.